T Lymphocytes

Cytotoxic T Lymphocytes

What are CTLs, or killer T-cells?
Cytotoxic T lymphocytes (CTLs) are a subset of αβT-cells that usually express the CD8 co-receptor and have the ability to directly kill infected cells or those that have become cancerous.

What is the role of CTLs in the immune system?
As a major part of the adaptive immune system, killer T-cells scan the intracellular environment in order to target and destroy infected cells. Small peptide fragments, representing the proteins inside a cell, are transported to the cell surface complexed to MHC molecules (pMHC), allowing killer T-cells to scan the cellular proteome for anomalies via their αβTCRs. Activation of CTL results in the release of cytotoxic granules, the release of lymphokines and the activation of apoptotic pathways via the FAS/FASL interaction to destroy the infected cell. Thus, CTL are critical to defence against viruses and tumours.